I tried using this service for the first time last night and was streaming video from my desktop that was running on Divx player. After about 5-10 minutes the audio starts to get out of sync, and it just gets progressively worse. I tried reducing video quality to 320x240 and putting audio on the lowest settings and it had the same problem.

I have a 15mb DL speed and a 1.5mb UL speed, and a high-end pc (quad core phenom, 4gb ram, gtx260 video, etc) so I don't believe my end should be an issue.